Effects of random fibre reinforcement on the density of granular materials

The growing need for the development of resilient track materials (including ballast) to cope with increasing train speed, load and frequency has led to a focus on optimizing performance and minimizing maintenance requirements. The use of fibres of random orientation has been shown to improve significantly the mechanical properties of sand. It is reasonable to expect that such random reinforcement will have similar effects on ballast, provided that a thorough understanding of the reinforcement mechanisms at both the micro and macro-scale is reached. This paper presents data based on macro-observations of fibre reinforced scaled ballast that suggest that fibres influence the micro-mechanical interactions governing the volume change of the mixture rather than influencing shear strength mobilization which is enhanced by the tensile capacity of the fibres in the mixture. In addition, the potential benefits of the proposed reinforcement technique in railway ballast are illustrated and discussed